Yeast and Mold
Yeasts and molds can cause deterioration and decomposition of foods, which is why food manufacturers will commonly test their products for TYM (Total Yeast and Mold). Certain species of yeast and mold, such as Aspergillus fumigatus, produce toxins that can cause potentially fatal infections. However, TYM tests are unable to differentiate between pathogenic, beneficial, and benign yeast and molds, making them poor indicators of safety.
A low TYM result does not mean a cannabis sample is free of pathogens. A high TYM result doesn’t mean a sample is harmful to consumers. This is especially true in cannabis, which has a diverse microbiome of beneficial microbes that are not harmful to humans. For example, many organic cannabis growers use Trichoderma, a fungus that can help plant nutrition and protect it from disease.
Still, many cannabis regulators require cannabis samples pass TYM testing before they can be sold in dispensaries. The most current version of the Cannabis Inflorescence and Leaf monograph published by the American Herbal Pharmacopoeia, which many states use to determine pass or fail criteria for microbial testing, recommends less than 10,000 CFU/g on cannabis plant material and 1,000 CFU/g on extracts.
Why Use qPCR Yeast and Mold testing on Cannabis?
Peer-reviewed studies have shown that qPCR testing methods are able to more accurately detect and quantify yeast and mold species present on a cannabis sample than culture-based methods. A total Yeast and Mold test looks for a specific DNA sequence that exists in all yeasts and molds. Because of this, the total Yeast and Mold test can detect all yeast and mold species, regardless of whether they grow in culture.
Culture-based tests can only detect the species that grow in a given medium and timeframe. Conversely, qPCR can more effectively exclude off-target microbial species, such as bacteria, which have been shown to grow in TYM culture medium.
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